The present invention concerns structures for axially bearing and locating the drive shaft of a magnetic-tape cassette recording and/or reproducing apparatus, when the latter is of the type in which the drive shaft extends horizontally and the cassette loading platform is oriented vertically so that an inserted cassette stands in an upright position in the apparatus.
With cassette machines of this type, a very important problem is to completely eliminate all axial play in the mounting of the drive shaft of the apparatus, i.e., the shaft carrying or serving as the capstan. Specifically, if during cassette machine operation the horizontally extending drive shaft shifts axially in either a regular or irregular fashion, corresponding fluctuations develop in the velocity with which the magnetic tape sweeps across the record and/or playback head of the machine, resulting in acoustic wow and/or flutter.
This is inherently a more serious problem in cassette machines with horizontally extending drive shafts, compared to those designed with upright drive shafts, because in the latter case the weight of the drive shaft itself and of its mounting structure contributes significantly to the axial stabilization of the location of the drive shaft.
In vertical-drive-shaft cassette machines of the front-loading type, the magnetic-tape cassette is pushed, in a direction parallel to the rotation axis of the drive shaft of the machine, onto the rotary spool-rotating pegs of the machine and, as this is done, the magnetic tape extending between the two spools of the cassette comes into engagement with the capstan part of the machine's drive shaft. In the past with this particular type of cassette machine, the bearing located at the same side as the drive pin of the machine is designed as an axial bearing applying axial-shift resisting force to the drive shaft from only one side thereof, inter alia by applying a spring biasing force against the peripheral surface of the bushing of the drive shaft, to eliminate axial shifting of the drive shaft in this manner.
That kind of axial bearing is, however, quite expensive to produce if the requisite degree of resistance to axial shifting of the drive shaft is really to be established by application of force to the drive shaft from one side. Furthermore, precisely because of the particular technique employed, the drive shaft must now turn against the circumferential component of this biasing force, i.e., against elevated frictional resistance. However, it is of course generally desirable not to work against unnecessarily high frictional resistance, and this is indeed quite important, for example, in the case of battery-powered cassette machines.